1. Field of the Invention
This invention relates to a carrier recovery loop. More particularly this invention relates to a long phase-locked loop for carrier recovery where the loop bandwidth is very small compared to the carrier frequency uncertainty.
2. Description of the Prior Art
Phase-locked loops are well known and do not require a detailed description. Such prior art phase-locked loops usually employed a closed loop which has the capability to acquire the carrier naturally.
Heretofore there were long phase-locked loops which employed closed loops with means for sweeping the frequency of the voltage controlled oscillator with the loop closed. Such prior art phased-locked loops required that the sweep be extremely slow in order to acquire the signal in a noisy environment.
Heretofore the wider the band of frequency uncertainty the longer it would take to sweep out the uncertainty bandwidth. Further, the saaller the closed loop bandwidth the slower the sweep must be conducted which requires longer sweep time.
It would be extremely desirable to provide a long phase-locked carrier recovery loop which is not constrained by the closed loop bandwidth and is capable of sweeping the frequency of uncertainty much faster than has been accomplished in the prior art.